Exploring the Link Between Ankylosing Spondylitis and Inflammatory Bowel Disease: A Retrospective Cohort Study

Background: Ankylosing spondylitis (AS) and inflammatory bowel disease (IBD) are chronic conditions with overlapping pathogenic mechanisms. The genetic predisposition and inflammatory pathways common to both diseases suggest a syndemic relationship. While some evidence points to a connection between the two conditions, other reports do not support this link. Objectives: To investigate the association between AS and the subsequent incidence of IBD. To identify potential risk factors and effect modifiers that contribute to this relationship. Methods: Utilizing the Chronic Disease Registry of Clalit Health Services, we conducted a retrospective cohort study of individuals diagnosed with AS between January 2002 and December 2018. We compared these patients with age- and sex-matched controls, excluding those with a prior diagnosis of IBD. Statistical analyses included chi-square and f-tests for demographic comparisons, and Cox proportional hazards models for evaluating the risk of IBD development, with adjustments for various co-morbidities and demographic factors. Results: The study included 5825 AS patients and 28,356 controls. AS patients demonstrated a significantly higher incidence of IBD with hazard ratios of 6.09 for Crohn's disease and 2.31 for ulcerative colitis, after multivariate adjustment. The overall incidence of IBD in the AS cohort was significantly higher compared to controls. Conclusions: AS patients exhibit a markedly increased risk of developing IBD. These findings advocate for heightened clinical vigilance for IBD symptoms in AS patients and suggest the need for a multidisciplinary approach to patient care. Further research into the shared pathogenic pathways is needed to develop personalized treatment strategies and improve patient management.